longevity/reliability of Rotax 80HP motors

[matt walsh]

Hi all, I'm am interested in your opinions/experiences regarding longevity/reliability of Rotax 80HP motors. Our 1996 Skyfox Gazelle runs the above motor which has completed about 2140hrs with no problems during our 4 years of ownership. Cylinder compressions have similar at each annual service, all AD's have been completed and no metal particles noted on drain plug or in filters. The engine has not given any problems or failures however the high cost of a toatl overhaul/rebuild will maynot be a good value proposition. I am particulary keen to undertake some interstate trips (already flown to William Creek and Flinders Ranges comfortably) and am thinking about reliabilty aspects during such a trip and over remote areas, with a motor having these hours.

 

Has anyone run their 80Hp's say beyound 3000hrs and without hesitation and problems? Any advice or issues to consider/manage with engines in this service bracket? Thanks, Matt Walsh, Gazelle 3478 Penfield Victoria. PS the aircraft is strictly private use, no school use.

 

 

[Guest Maj Millard]

If all parameters are within specs and no metal is evident on filter element or magnetic plug, then things should continue to be fine. I am assuming the engine still makes proper RPMs and produces normal power, with oil pressure in range. Would be good to check gearbox, and oil pump. The oil pump surfaces for any gouges , grooves or marks. You could also increase the frequency of oil changes and metal contamination checks if you wish.

 

Remember the 80 HP is a low compression engine, and for this reason was the basis for the 914 Turbo. With the turbo producing another 35 HP at the top end. This indicates to me that the base engine, rods, crank etc are way stronger than intended for 80 HP. The 100 HP engine is a 10 to 1 high compression engine, and therefore not suited to turbocharging.

 

I am told reliably that what gets them in the end, is carbon build up on the valves/ valve seats which causes a cylinder to miss. A normal top end valve-grind at that point, and away you go again !.........great little engines that run beautifully, and we are very lucky to have them....................Maj........

 

 

[matt walsh]

Maj, thanks for your comments and advice. I'm reading from your words that operating reliably and confidently beyond current 2130 hrs, with all checks being ok, can be expected. Cheers Matt Walsh

 

 

[mnewbery]

Check the radial alingment and spacing between the balance (cheek) weights on the crank. If they are different by more than a millimetre (look at the rotax manual for the limit) the crank is twisted and/or bent. This comes from running regular unleaded petrol and is to be expected. See below.

 

http://www.avweb.com/news/maint/rotax_overhaul_options_208438-1.html

 

From that article

 

When Lockwood's Dean Vogel heaved an old crankcase up on the overhaul bench, we could easily see why it's spec'd for new only. Two of the counterweight cheeks were visibly misaligned, probably the result of detonation from low-octane fuel. "It's not likely to break," Vogel said, "but it will twist. We see this from time to time."

[Guest Crezzi]

The OP refers to the 80hp 912 which is designed to run on regular unleaded mogas (min 90RON)

 

Cheers

 

John

 

 

[Downunder]

Why not start a replacement/overhaul program Matt?

 

Spread it over a couple of years. Overhaul the heads first. The maybe replace the oil pump............

 

Spreads your costs out and improves reliability..........